Radiotelegraphy



Jun; 24, 1930. E. F. ALEXANDERSON I 1,768,433

RADIQTELEGRAPHY Filed Au 9; 192a Invent on Enns't Ff \A/ Alexandewson,

His Attor'ne y Patented June 24, 1930 UNITED STATES PATENT OFFICE.

ERNST F. W. ALEXANDERSON, OF SGHENECTADY,'NEW YORK, ASSIGNOR 'I'OGENEIRAL ELECTRIC COMPANY, A. CORPORATION OF NEW YORK RADIOTELEGRAPHYvApplication filed August 9, 1926. Serial No. 128,268.

My invention relates to radiotelegraphy, and has for its principalobject the provision of an improved system that is capable of accuratelytransmitting signals at a comparatively high rate of speed,

It is customary to supply energy to an antenna from a high frequencysource and to control this energy by change in the saturation of avariable impedance device s ich as a magnetic amplifier which isconnected to the antenna in series or parallel with the high frequencysource and is provided with a saturation or exciting winding energizedin accordance with the signals to be transmitted. This method ofcontrolling the energy supplied to the antenna involves the use of meansfor controlling the circuit of the exciting winding. Such circuit control means should be capable of clearly defining the periods ofenergization and deenergizataion of the exciting 'winding and should becapable of opening and closing at a high rate of speed in order topermit the rapid transmission of signals. Various circuit control meanshave been provided in the past for controlling thesaturation of theimpedance device or magnetic amplifier but the operation of manyof thesecontrol means has not been altogether satisfactory for the reason thatthey either do not operate with sufficient rapidity or are incapable ofcontrolling currents large enough to saturate the magnetic amplifier.

'In patent No 1,675,987, of Albert H. Mittag, issued July 3, 1928, isdisclosed a signal control system wherein current is transmitted from adirect current source to the exciting windingof a magnetic amplifierthrough a vapor electric device provided with grids for controlling thetransmission of current between its cathode and its anodes, on of theanodes being connected in series with the exciting winding and the otheranode being connected ina circuit independently of the exciting winding.Dur

ing operation of this system, potentials varying in accordance with thesi als to be transmitted are applied to the grids, and the currents ofthe device are shifted from one anode to another at the beginning of thesignal and in the'reverse direction at the end of the signal. As statedin the aforesaid application, this system is capable of transmittingsignals at a'rate corresponding to approximately 250 words per minute. Ihave found that this rate may be increased materially by utilizingcurrent supplied from a high frequency source and rectified by a vaporelectric device provided with grids energized in accordance with thesignals to be transmitted.

vMy invention will be better understood from the following descriptionwhenconsidered in accordance with the accompanying drawings and itsscope will be pointed out in the appended claims. 7

Referring to the drawings, Fig. 1 shows a signal transmitting systemwherein my invention has been embodied; and Fig. 2 shows a modifiedembodimentof the invention.

.Fig. 1 shows a signal control system wherein current is supplied from ahigh fre quency source 1Vto a consumption circuit shown as an antenna 2.This current iscontrolled'by a magnetic amplifier 8 which is connectedto the secondary circuit of an antenna transformer 4 through a condenser5 and is provided with oppositely wound operating coils 6 and 7 and withan exciting or saturation coil 8. the magnitude of the current suppliedto the antenna 1 is determined by the magnetic amplifier impedance whichis controlled by the current transmitted through the saturation winding8. r

Current is supplied to the winding 8 from a suitable high frequencysource through supply busses 9, a transformer 10 and a vapor electricdevice 11. The device 11 is provided with anodes 12 and 18, grids 14 and15, exciting electrodes 16 and 17, and a vaporizable cathode 18. It willbe observed that the cathode 18 is-connected to, the anodes 12 and 13through an impedance device 19, excitingcoil 8 and opposite halves ofthe secondary circuit of the transformer 10, is connected to theexciting electrodes 16 and 17 through a source of excitation shown as aWith these connections,

generator 20, and is connected to grids 14 device 22 and throughimpedances 23 and 241- respectively. A source 25 is arranged to beconnected in shunt to the source 21 and impedance device 22 by means ofa switch or key 26 which may be operated either manually or in any othersuitable manner.

WVith the busses 9 energized and the con nections as illustrated, nocurrent is supplied to the exciting coil 8 for the reason that the grids1 1 and 15 are charged to a negative potential by the source 21. Uponclosure of the key 26, however, the grids 142 and 15 are charged to apositive potential by the source 25 and current is immediatelytransmitted through the device 11 to the exciting coil 8, therebyproducing an immediate increase in the current supplied from the source1 to the antenna 2. \Vhen the key 2-6 is opened, the antenna current isrestored to its normal value. The closing and opening of the key 26 thusinitiates and terminates the signal.

The speed at which it is possible to transmit signals is dependent onthe frequency of the current supplied through the busses 9. This is truebecause a negative potential on the grids 14: and 15 will prevent thestarting of current through the device 11 but will not stop this currentafter it has once started. Each time the polarities of the anodes 12 and18 are reversed, however, control by the grids 1d and 15 is secured. Thetime lag between operation of the key 26 and change in the current ofthe coil 8 will therefore tend to decrease as the frequency of thecurrent supplied through busses 9 is increased. Thus, with currentsupplied to the transformer 10 at a frequency of about 2,000 cycles, forexample, I have found that signals may be readily sent at a speed whichcorresponds to more than 300 words per minute. The advantages of myinvention, however, are not limited to this frequency but are realizedin various degrees as the frequency of the control current is changed invalue. The term hi 'h frequency as used throughout this app ication istherefore intended to mean any frequency whereby the time lag betweenoperation of the control key and change in the signal current is madeshort enough to materially increase the rate at which signals may besent by other devices available to those skilled in the art.

Fig. 2 shows a signal control system which differs from that of Fig. 1in that the source 25 is shown as a direct current generator 27 and inthat control of the negative potential applied to the grids 14 and 15 bythis generator is effected by control apparatus comprising atransformer. 28, a vapor electric device 29, a control key 30, and animpedance device 81 which is connected between the generator 27 and thegrids 14 and 15 and is arranged to produce a counterelectromotive forcedependent on the current transmitted from a high frequency source 82 tothe device 81. Current from the source 32 may also be supplied to thetransformer 10 through which the exciting coil 8 is energized. Theconnections of the device 29 are substantially the same as thosedescribed in connection with Fig. 1, and it will be readily understood,without detailed explanation, that current is supplied to the device 31only when the key is in its closed position and that the effect of thiscurrent is to produce a counter-electromotive force whereby thepotentials of grids 14 and 15 are changed from a negative to a positivevalue.

The embodiments of the invention illustrated and described herein havebeen selected for the purpose of clearly setting forth the principlesinvolved. It will be apparent, however, that the invention issusceptible of being modified to meet the difierent conditionsencountered in its use and I therefore aim to cover by the appendedclaims all modifications within the true spirit and scope of myinvention. 5,

VJ hat I claim as new and desire to secure by Letters Patent of theUnited States, is:

1. The combination of a consumption device, a variable impedance deviceconnected to said consumption device, a source of alternating current, avapor electric device previded with a cathode and anode connectedbetween saidsource and said impedance device and with a grid forcontrolling the current transmitted to said impedance device, meansconnected between said grid and cathode for biasing said grid to anegative potential, and means connected to said source for producing anelectromotive force which is opposed to said negative potential wherebysaid grid 'is charged to a positive potential.

2. The combination of a consumption de vice, a variable impedance deviceconnected to said consumption device, a source of alternating current, avapor electric device provided with a cathode and anode connectedbetween said source and said impedance device and with a grid forcontrolling the current transmitted to said impedance device, adirectcurrent source connected between said grid and cathode for biasingsaid grid to a negative potential, a resistor connected in circuit withsaid direct current source, and means connected between said alternatingcurrent source and said resistor whereby a positive potential may beapplied to said grid.

3. The'combination of a consumption d vice, a variable impedance deviceconnected to said'consumption'device, a source of alternating current, avapor electric device provided with a cathode and anode connectedbetween said source and said impedance -device and with a grid forcontrolling the current transmitted to said impedance device, a directcurrent source connected be,- tween said grid and cathode for biasingsaid grid to a negative potential, a resistor connected in circuit withsaid direct current source, and means comprising a vapor electric deviceconnected between said alternating current source and said resistorwhereby a pdpsitive potential may be applied to said r1 g 4:. Thecombination of an antenna, a

source of current connected to said antenna, a variable impedance devicearranged to control the current supplied from said source to saidantenna, and means for controlling the impedance of said devicecomprising a hi h frequency source independent of said rst source, andvapor electric means provided with an anode and cathode connectedbetween said device and said high frequency source and with a gridarranged to be energized in accordance with the signals to betransmitted by said antenna.

5. The combination of a consumption device, a variable impedance deviceconnected to said consumption device, means for supplying controlcurrent to said impedance device including a vapor electric devicehaving an anode, a'cathode and a grid, means for supplying highfrequency alternating potential to the anode of said device, means connected between said grid and cathode for charging said grid to anegative potential and means for causing a positive potential. to beapplied to said grid in accordance with desired signals, the frequencyof said alternating potential being sufficiently high to permitoperation of said last means at high signaling speed. I 40 In witnesswhereof, I have hereunto set my hand this 6th day of August, 1926.

ERNST F. W. ALEXANDERSON.

